Locksmith Job - Parktown North, GP, 2193

We have a door on our corner property which leads to Fourth Street. The lock on this door has several bolts, which can be turned approx. 150 degrees to the left after inserting the key to open the lock before it blocks. We have had this in the past, but it always worked again. Now I can move the key but the lock does not move and the door cannot be opened and we need your help.